Cell reselection and handover with multimedia broadcast/multicast service

ABSTRACT

A method and apparatus for providing wireless communication services, (e.g., multimedia broadcast multicast services (MBMS)), are disclosed. A wireless transmit/receive unit (WTRU) detects a plurality of target cell evolved Node-Bs (eNodeBs) that neighbor a serving cell eNodeB. The WTRU evaluates cell reselection criteria and determines a neighboring target cell eNodeB to reselect. The WTRU receives and reads master information block (MIB) and system information messages of the neighboring target cell eNodeB, and confirms that the determined neighboring target cell eNodeB is not part of a multimedia broadcast single frequency network (MBSFN). The WTRU identifies the neighboring target cell eNodeB to the serving cell eNodeB. The WTRU then receives and reads MIB messages of the neighboring target cell eNodeB again to determine whether the system information has changed and, if so, the WTRU reads the system information and reselects to the neighboring target cell eNodeB, which provides the wireless communication services.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/915,030 filed Apr. 30, 2007 and U.S. Provisional Application No.60/944,548 filed Jun. 18, 2007, which are incorporated by reference asif fully set forth.

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

One of the main problems when a wireless transmit/receive unit (WTRU) isreceiving multimedia broadcast multicast services (MBMS) is maintainingthe service continuity and minimizing the delay during handover and cellreselection. Furthermore, the service continuity must be maintained andthe delay must be minimized when the WTRU moves across from a multimediabroadcast single frequency network (MBSFN) service area to a non-MBSFNservice area, but within the same MBMS service area.

Different steps that need to be considered when an idle mode WTRUreceiving an MBMS transmission in an MBSFN service area approaches theborder of the MBSFN service area, have been raised. The stepsinclude: 1) detect that the WTRU is approaching the border of the MBSFNservice area; 2) move to active mode; and 3) request the reception ofthe MBMS service in single cell mode point-to-point (PTP). The targetcell evolved Node-B (eNodeB) also has to check whether the requestedservice is available or not and, if not, 4) join the multicastdistribution tree for the MBMS service; and 5) finally start providingMBMS data to the WTRU in single cell mode.

While a few high level system solutions have been suggested, a moreintegrated solution that would help minimize delay and maintain theservice continuity is needed. Accordingly, it is desirable to enhancethe transit from a non-MBSFN area to another non-MBSFN service area orto an MBSFN service area, as well as reselection from an MBSFN servicearea to a non-MBSFN service area.

SUMMARY

A method and apparatus for providing wireless communication services,(e.g., MBMS), are disclosed. A WTRU detects a plurality of target celleNodeBs that neighbor a serving cell eNodeB. The WTRU evaluates cellreselection criteria and determines a neighboring target cell eNodeB toreselect. The WTRU receives and reads master information block (MIB) andsystem information messages of the neighboring target cell eNodeB, andconfirms that the determined neighboring target cell eNodeB is not partof an MBSFN. The WTRU indicates the determined neighboring target celleNodeB to the serving cell eNodeB. The WTRU then receives and reads MIBmessages of the neighboring target cell eNodeB again to determinewhether the system information has changed and, if so, the WTRU readsthe system information and reselects to the neighboring target celleNodeB. The WTRU then sends a cell update message with capabilityinformation and service requirements to the neighboring target celleNodeB, which in turn sends a cell update confirmation message to theWTRU indicating that the target cell eNodeB is ready to start providingthe wireless communication services.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description, given by way of example and to be understood inconjunction with the accompanying drawings wherein:

FIG. 1A is a signal flow diagram that shows a cell reselection from anMBSFN cell to a non-MBSFN cell in which a WTRU receives neighbor cellinformation from a serving cell eNodeB;

FIG. 1B is a signal diagram similar to FIG. 1A except that an indicationthrough a broadcast or any other message is sent to the WTRU indicatingthat the target cell eNodeB is ready to start MBMS service;

FIG. 2A is a signal flow diagram that shows a cell reselection from anMBSFN cell to a non-MBSFN cell in which in which a WTRU does not receiveneighbor cell information from a serving cell eNodeB;

FIG. 2B is a signal diagram similar to FIG. 2A except that an indicationthrough a broadcast or any other message is sent to the WTRU indicatingthat the target cell eNodeB is ready to start MBMS service;

FIG. 3A is an exemplary signal diagram showing a WTRU moving from anon-MBSFN cell to a non-MBSFN cell where a neighbor list for MBMS cellsis transmitted by a serving cell;

FIG. 3B is an exemplary signal diagram showing a WTRU moving from anon-MBSFN cell to a non-MBSFN cell where a neighbor list for MBMS cellsis not transmitted by a serving cell;

FIG. 4 is a block diagram of a WTRU; and

FIG. 5 is a block diagram of an eNodeB.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

In the current work group (WG) radio access network 2 (RAN2), there ismuch debate as to whether a neighbor cell list might be needed for cellreselection. While a neighbor cell list is not considered mandatory forcell reselection, it is still uncertain if there is a need to indicatespecific intra-frequency neighboring cells to improve performance oftheir detection. This principle of being able to signal specificintra-frequency neighboring cells is used to improve MBMS servicecontinuity performance. There are also cases and scenarios in which theneighbor list is not being transmitted by the serving cell.

This application will cover two scenarios, each for cell reselection andhandover cases with MBMS services ongoing. For both scenarios, it isassumed that the WTRU is camped on a cell in the MBSFN area before thereselection procedure begins.

Cell Reselection

When a neighbor cell identity (ID) list information is transmitted by aserving cell eNodeB, the capability information of the neighbor MBMScells may or may not be transmitted by the serving cell to save onresources.

At the border of the MBSFN areas, the neighbor cells should be signaledalong with an indicator (one bit or more) signaling whether thoseneighbor cells are part of the MBSFN area, MBSFN guard area or non-MBSFNarea. Thus, the border eNodeBs need to be configured with thisinformation. Alternatively each of the eNodeBs could find informationabout its neighbor cells from an access gateway (AGW), which shouldcontain the information when the MBSFN area is configured. Alternativelythe eNodeBs could also request the neighboring cell capabilityinformation periodically from the AGW to take care of any updates orchanges in the MBSFN area.

Also knowing the neighbor cell information, the serving cell couldfigure out that it is a border cell and through its broadcast messagesstill indicate that it is a border/edge cell of the MBSFN area. Thus,only eNodeBs in the edge of an MBSFN area would be involved and the WTRUwould expect that the cell it may reselect to may be part of the MBSFNguard area or a part of the non-MBSFN area and could potentially usethis information to make its reselection and handover procedures morerobust.

A WTRU which is at the edge of such a MBSFN cell would thus have thelist of the neighbor cells and the capability information for each ofthose cells.

In such a scenario when it does a cell reselection procedure it wouldfirst give weight to those cells at the edge which are part of the MBSFNarea. If it does not find any such cell, it would then give priority tothose cells which are part of the MBSFN guard area. Finally, it wouldtry and reselect to a cell from the non-MBSFN area based on cellreselection procedures, such as those disclosed in commonly assignedU.S. Provisional Application 60/894,588, filed on Mar. 13, 2007, whichis incorporated by reference as if fully set forth. The WTRU knowing itsown service requirements would not reselect to those cells (if any)which are not part of the MBSFN area nor are part of the MBMS servicearea. In case the network would like to control the reselectionprocedure, (e.g., it may not want the WTRU not to reselect to anyparticular cell due to cell loading or other reasons), it can indicate avery high offset for that (a particular) cell or include a neighbor cellblacklist or probably even a white list with only certain neighbors.

Handover

In a first handover scenario, a normal handover occurs where the WTRU isin active state and performs a normal WTRU controlled handover to atarget cell eNodeB. If the WTRU wants to handover to a cell in anon-MBSFN area, the WTRU capabilities and requirements could be passedin the handover request message from the serving cell eNodeB to thetarget cell eNodeB, which would then have the time to join the multicastdistribution tree and prepare for a PTP MBMS service. If the target celleNodeB is not in such a position, it could reject the handover requestand the WTRU would have an opportunity to handover to a different targetcell eNodeB.

In a second handover scenario, a network directed handover occurs whereeither the WTRU could be in the idle state, and then transition to anactive state once it detects that the serving cell eNodeB it is campedon is a border MBSFN cell, and send its measurements to the network, orthe WTRU could already be in an active state. Based on the measurementssent, the network could direct the WTRU to handover to a particulartarget cell eNodeB providing the required service.

As mentioned before, the WTRU could initially be in an idle state, butthen contact the target cell eNodeB and transition to an active state byestablishing a radio resource control (RRC) connection with the servingcell eNodeB, when it detects that it is in a border cell of the MBSFNarea, in accordance with one of the first and second handover scenarios,(e.g., the target cell eNodeB or reading SIBs), or via an explicitindicator that is broadcast that indicates that the serving cell eNodeBlies in the border of the MBSFN area. RRC connection establishmentmessages may be enhanced to indicate that the WTRU is currentlyreceiving MBMS traffic.

Once the WTRU transitions to an active state or for a WTRU already inthe active state, the WTRU may send measurement reports to the networkindicating the signal quality it observes. Once the serving cell eNodeBis made aware of the presence (or measurements) of the WTRU, the servingcell eNodeB monitors the measurements from the WTRU, and decides whetherto command/redirect the WTRU to another cell where it can get the PTPMBMS services.

If the serving cell eNodeB decides to command/redirect the WTRU toanother cell, (i.e., target cell eNodeB), where it can the PTP MBMSservices, the serving cell eNodeB contacts the target cell eNodeBsending it the appropriate parameters to prepare for the MBMS PTPservice. The target eNodeB prepares the MBMS PTP service for the WTRU,and sends a signal confirming so back to the serving cell eNodeB. Theserving cell eNodeB then commands/redirects the WTRU to access thetarget eNodeB. The WTRU accesses the target eNodeB it was commanded toaccess, and receives the MBMS PTP service.

Furthermore, the cell reselection or handover procedures may be furtherhastened by not repeating the generic bootstrapping procedure for MBMSon every cell. For this, the WTRU would need to store the key Ks andother pertinent security information for not only the serving cell, butalso for the last few camped cells. This could also be left asimplementation option for the WTRU.

Next described are methods whereby the TA concept may be used tofacilitate MBMS service continuity. Note that these methods may be usedeither in conjunction with or independent of the methods to ensure MBMSservice continuity that were previously described in this document.

Design and Use of Tracking Areas to Facilitate MBMS Service Continuity

Tracking areas (TAs) are designed such that a MBSFN cell that is at theedge of the MBSFN area, (i.e., the border cell), will belong to a TAwhich is different than the tracking areas for the non-border cells,(i.e., the inner cells), of the MBSFN area.

Similarly, TAs are designed such that a cell that is in the MBSFN guardarea will belong to a TA which is different than the tracking areas forthe cells belonging to MBSFN area. Upon moving into a border cell of theMBSFN area, or into a cell in the guard MBSFN area, the WTRU willtrigger a TA update message (since it will be moving into another TA, bydesign).

The TA update message may include an indication of whether the WTRU isreceiving MBMS services, the type of MBMS service it is receiving, (PTPor MBSFN), and/or any other configuration parameters or contextinformation related to the MBMS service.

Alternatively to sending the above TAU information, only informationthat has changed from current MBMS service may be included so that theeNodeB can be informed and prepare in advance. Otherwise, there is noneed to repeat the information without change to eNodeB again. This cansave uplink signaling overhead.

When the WTRU is inside the edge cell, one alternative to send TAUmessage is to only include critical information such as WTRU beingcurrently at edge cell, or maybe mobility or trajectory trend (servingeNodeB can know if WTRU is still moving out of MBSFN area or may belingering inside the MBSFN area). This information is sufficient for theserving cell eNodeB to know in advance if handover preparation needs tobe triggered or not. The uplink signaling overhead can thus beminimized.

A measurement report may be sent along with the TA update, or at anytime after the WTRU moves into the cell. This measurement report would areport that is sent after the handover is done and is used by the edgecell for future handovers. Upon receiving the TA update, (with theoptional indication or context information of MBMS services being usedby the WTRU), the eNodeB will execute the switch from SFN MBMS servicesto PTP MBMS services. For example, if the eNodeB is in the MBSFN guardarea, the eNodeB will establish PTP MBMS services first, by paging theWTRU which in turn will request an RRC connection, and the setupprocedure continues from there on. If the eNodeB is in the MBSFN borderarea, the eNodeB will request the preparation of the MBMS resources froma suitable target cell eNodeB, (e.g., based on WTRU measurement reportsand other admission criteria), and then command/redirect the WTRU to thetarget cell eNodeB, similar to what has been previously described forthe other scenarios/cases of this document.

In the current WG RAN2, there is much debate as to whether a neighborlist may be needed for cell reselection. It is under study if there is aneed to indicate specific intra-frequency neighboring cells to improveperformance of their detection. Therefore, this principle of being ableto signal specific intra-frequency neighboring cells to improve MBMSservice continuity performance may be utilized. Cases and scenarioswithout the neighbor list being transmitted by the serving cell may alsobe considered.

This application is directed to the handover and reselection to and froman MBSFN and a non-MBSFN area. In all cases, the WTRU depends on thenetwork to transmit some information about the neighbor cellcapabilities either through the broadcast message or some dedicated RRCsignaling message in the serving cell or the target cell. Beforehandover, the WTRU tries and informs the target cell either through theserving cell or by directly transmitting a message in the target aboutthe services it requires, giving the target cell the opportunity toprepare for the reselection or handover procedure.

FIG. 1A is a signal flow diagram that shows a cell reselection scenarioin a wireless communication system 100 including a WTRU 105, a servingcell eNodeB (MBSFN area) 110, a target, (i.e., neighbor), cell eNodeB(non-MBSFN area) 115 and an AGW 120. The WTRU 105 moves from the servingcell eNodeB 110 in an MBSFN area to the target cell eNodeB 115 in anon-MBSFN area.

In the cell reselection scenario of FIG. 1A, neighbor cell information,(e.g., a neighbor cell list), and capability information for MBMS cellsin an MBSFN area, is transmitted by the AGW 120 to the serving celleNodeB 110 (step 125). Alternatively, the serving cell eNodeB 110 may bepreconfigured with the neighbor cell information, (e.g., a neighbor celllist), and capability information for MBMS cells in an MBSFN area, suchas via a periodic message. The serving cell eNodeB 110 then transmitsneighbor cell information to the WTRU 105 (step 130). In step 135, theWTRU 105 evaluates cell reselection criteria and determines aneighboring target cell to reselect. Before it starts the reselectionprocedure, the WTRU 105 first sends a random access channel (RACH)preamble or RACH message to the current serving cell eNodeB 110 it iscamped on (step 140), indicating the neighbor cell it is planning toreselect, (i.e., the target cell eNodeB 115). Also, if possible,dedicated signatures may be reserved for this purpose to minimize thecell reselection interruption time. In step 145, the serving cell eNodeB110 sends a signal to the target cell eNodeB 115 including the ID,(e.g., international mobile subscriber identity (IMSI), temporary mobilesubscriber identity (TMSI)), of the WTRU 105 and indicating that theWTRU 105 requires a PTP MBMS service.

Still referring to FIG. 1A, in step 150, the target cell eNodeB 115determines whether it has the required PTP MBMS service available. Ifnot, the target cell eNodeB 115 sends a signal to the AGW 120 requestingthat the AGW 120 join the target cell eNodeB 115 to a multicastdistribution tree for providing the required service (step 155), wherebythe AGW 120 provides MBMS information to the target cell eNodeB 115,which in turn provides the MBMS information to the WTRU 105. After theAGW 120 joins the target cell eNodeB 115 to the multicast distributiontree (step 160), the AGW 120 may signal an explicit positiveacknowledgement (ACK) to the target cell eNodeB 115 (step 165), or thiscan be assumed implicitly through no signalling. If the target celleNodeB 115 is not joined to the multicast distribution tree, then theWTRU 105 would be appropriately informed.

Alternatively, the WTRU 105 could, along with indicating, to the servingcell eNodeB 110, the target cell eNodeB 115 that it is going to camp on,also send neighbor cell capability information to the serving celleNodeB 110. The serving cell eNodeB 110, knowing the servicecapabilities of the target cell eNodeB 115, may determine whether thetarget cell eNodeB 115 is capable of providing the PTP MBS service and,if not, the serving cell eNodeB 110 may forward the WTRU ID along withthe services required to the target cell eNodeB 115.

Alternatively the WTRU 105 may just send a message to the currentserving cell eNodeB 110 it is camped on, indicating the target celleNodeB 115 it is planning to reselect as mentioned before. The servingcell eNodeB 110 could have information of the target cell eNodeB 115from the network, and thus knowing the service capabilities of thetarget cell eNodeB 115, the serving cell eNodeB 110 may determinewhether the target cell eNodeB 115 is capable of providing the serviceand, if not, the serving cell eNodeB 110 may forward the WTRU ID alongwith the services required to the target cell eNodeB 115. After sendinga signal to the serving cell eNodeB 110, the WTRU 105 starts thereselection procedure to the cell in a non-MBSFN area.

Each cell in an MBMS service area transmits MIB and system informationmessages at a periodic rate. The MIB and system information messagesinclude information indicating whether the cell is part of an MBSFN areaor whether the cell only supports a PTP service. Thus, when the WTRU 105reads the MIB and system information messages that are transmitted bythe target cell eNodeB 115 (step 170), the WTRU 105 can confirm that thenew cell it is planning to reselect is not part of an MBSFN area (step175). Alternatively, only a cell in the MBMS PTP area or the MBSFN areacan transmit the information as to whether the cell is part of the MBSFNarea or not. Once the WTRU 105 has finishes reading the MIB and systeminformation messages (step 170), the WTRU 105 reselects to the targetcell eNodeB 115 (step 180) and sends a cell update message to the targetcell eNodeB 115 indicating its TMSI or some other ID, its owncapabilities and its requirements for a PTP MBMS service (step 185).

The target cell eNodeB 115, having been pre-informed of the requirementsof the WTRU 105, should be capable of supporting the MBMS PTP serviceand confirming this support by transmitting a cell update confirmmessage to the WTRU 105. If the target cell eNodeB 115 is not able tojoin the multicast distribution tree, then it can indicate this to theWTRU 115 in the cell update confirm message (step 190). Thus, the WTRU105 would have the choice to reselect to another cell which has thecapability using its prior information, or initiate another newreselection procedure altogether, but this may introduce additionaldelays. Alternatively, it is proposed that the target cell eNodeB 115may redirect the WTRU 105 to another cell eNodeB that is capable ofproviding the PTP MBMS service. The target cell eNodeB 115 may utilizethe latest WTRU measurement report information (if available) in orderto select the eNodeB to which the WTRU 105 would be redirected, e.g.,the WTRU 115 would send the measurement report when it sent the cellupdate message, or at any other time.

The above procedures are the same if the WTRU 105 had reselected to acell in an MBSFN guard area, but the interruption time would be shortersince a cell in the MBSFN guard area would find it easier to join themulticast distribution tree, since it should already be synchronizedwith the MBSFN network.

FIG. 1B is a signal diagram similar to FIG. 1A except that an indicationthrough a broadcast or any other message is sent to the WTRU indicatingthat the target cell eNodeB is ready to start MBMS service (step 195).

FIG. 2A is a signal flow diagram that shows a cell reselection scenarioin a wireless communication system 200 including a WTRU 205, a servingcell eNodeB (MBSFN area) 210, a target, (i.e., neighbor), cell eNodeB(non-MBSFN area) 215 and an AGW 220. The WTRU 205 moves from the servingcell eNodeB 210 in an MBSFN area to the target cell eNodeB 215 in anon-MBSFN area but, unlike the cell reselection scenario of FIG. 2A, theneighbor cell information and capability information for the MBMS cellsis not transmitted by the serving cell to the WTRU.

When neighbor cell information, (e.g., a neighbor cell identity (ID)list), is not transmitted, the serving cell eNodeB 210 in the MBSFN areamay or may not have the neighbor cell information and capabilityinformation. It is first assumed that the serving cell eNodeB 210 doesnot have any information of the neighbor cells (step 225). In thisscenario, the WTRU 205 would not know whether the cell to which it isplanning to reselect is part of the MBSFN area or not, and hence theWTRU 205 will have to detect potential neighboring target cell eNodeBs,evaluate cell reselection criteria and, determine a target cell eNodeB215 to reselect (step 230). Based on its determination, the WTRU 205will have to proceed with reading the MIB and system informationmessages (step 235).

Alternatively, even if the neighbor cell information is not provided,the serving cell eNodeB 210 could still indicate through its broadcastmessages if it is a border/edge cell of the MBSFN area. Thus, the WTRU205 would expect that the target cell eNodeB 215 it might reselect tomay be part of the MBSFN guard area or a part of the non-MBSFN area.

It is still proposed though that all the cells in a MBMS service areashould transmit the information as to whether it is part of a MBSFNarea, MBSFN Guard Area or whether it only supports a PTP service in itssystem information messages. Thus, when the WTRU 205 reads the systeminformation messages that are transmitted by target cell eNodeB 215, theWTRU 205 confirms that the new cell, (i.e., target cell eNodeB 215),that it is planning to reselect is not part of the MBSFN area (step240). Alternatively, only a cell in the MBMS PTP area or the MBSFN areacan transmit the information indicating whether the cell is part of theMBSFN area or not.

In step 245, the WTRU 205 first sends a random access channel (RACH)preamble or RACH message to the current serving cell eNodeB 110 it iscamped on (step 245), indicating the neighbor cell it is planning toreselect, (i.e., the target cell eNodeB 115). Also, if possible,dedicated signatures may be reserved for this purpose to minimize thecell reselection interruption time. In step 250, the serving cell eNodeB210 sends a signal to the target cell eNodeB 215 including the ID,(e.g., international mobile subscriber identity (IMSI), temporary mobilesubscriber identity (TMSI)), of the WTRU 205 and indicating that theWTRU 205 requires a PTP MBMS service.

Still referring to FIG. 2A, in step 255, the target cell eNodeB 215determines whether it has the required PTP MBMS service. If not, thetarget cell eNodeB 215 sends a signal to the AGW 220 requesting that theAGW 220 join the target cell eNodeB 215 to a multicast distribution treefor providing the service (step 260). After the AGW 220 joins the targetcell eNodeB 215 to the multicast distribution tree (step 265), the AGW220 may signal an explicit positive acknowledgement (ACK) to the targetcell eNodeB 215 (step 270), or this can be assumed implicitly through nosignaling. If the target cell eNodeB 215 is not joined to the multicastdistribution tree, then the WTRU 205 would be appropriately informed.

Alternatively, the WTRU 205 could, along with indicating, to the servingcell eNodeB 210, the target cell eNodeB 215 that it is going to camp on,also send neighbor cell capability information to the serving celleNodeB 210. The serving cell eNodeB 210, knowing the servicecapabilities of the target cell eNodeB 215, may determine whether thetarget cell eNodeB 215 is capable of providing the PTP MBS service and,if not, the serving cell eNodeB 210 may forward the WTRU ID along withthe services required to the target cell eNodeB 215.

Alternatively, the WTRU 205 may just send a message to the currentserving cell eNodeB 210 it is camped on, indicating the target celleNodeB 215 it is planning to reselect as mentioned before. The servingcell eNodeB 210 could have information of the target cell eNodeB 215from the network, and thus knowing the service capabilities of thetarget cell eNodeB 215, the serving cell eNodeB 110 may determinewhether the target cell eNodeB 215 is capable of providing the serviceand, if not, the serving cell eNodeB 210 may forward the WTRU ID alongwith the services required to the target cell eNodeB 215. After sendinga signal to the serving cell eNodeB 210, the WTRU 205 starts thereselection procedure to the cell in a non-MBSFN area.

In step 275, the WTRU 205 then reads the MIB messages again to confirmthat the system information has not changed since the last reading (step275). This may be required since by sending a message to serving celleNodeB 210 (steps 245 and 250) after reading the system informationmessages received from the target cell eNodeB 215, there is a slighttime gap introduced between the reading of the MIB and systeminformation messages, and the sending the cell update message. However,since it is highly likely that the system information messages would nothave changed since the last reading, the slight delay introduced shouldnot be a problem. Hence the WTRU 205 should not face much delay inreselection. If there are any changes to the system information, theWTRU reads the system information messages and reselects to the targetcell eNodeB (step 280).

Once the WTRU 205 has finished reading the system information messages,the WTRU 205 can send a cell update message to the target cell eNodeB215 indicating its TMSI or some other ID, its own capabilities and itsrequirements for a PTP MBMS service (step 285).

The target cell eNodeB 215, having been pre-informed of the requirementsof the WTRU 205, should be capable of supporting the MBMS PTP serviceand confirming this support by transmitting a cell update confirmmessage to the WTRU 205 (step 290). If the target cell eNodeB 215 is notable to join the multicast distribution tree, the target cell eNodeB 215can request the packets from the serving cell eNodeB 210, and theserving cell eNodeB 210 could forward the MBMS packets to the targetcell eNodeB 215. The target cell eNodeB 215 could then forward them tothe WTRU 205 until it joins the multicast distribution tree.

Alternatively, even if the target cell eNodeB 215 has not joined themulticast distribution tree, it could wait till it has joined the tree ,proceed with the cell update confirm message informing the WTRU 205 thatthe MBMS service would resume within some period of time and then resumethe service when finally it has required MBMS service. This optionthough could increase the amount of delay.

Alternatively, it is proposed that the target cell eNodeB 215 mayredirect the WTRU 205 to another cell eNodeB that is capable ofproviding the PTP MBMS service. The target cell eNodeB 215 may utilizethe latest WTRU measurement report information (if available) in orderto decide on the cell eNodeB to which the WTRU 215 would be redirected,e.g., the WTRU 215 would send the measurement report when it sent thecell update message, or at any other time.

The above procedures of the second reselection scenario are the same ifthe WTRU 215 had reselected to a cell in a MBSFN guard area, but theinterruption time should reduce since a cell in the MBSFN guard areashould find it easier to join the multicast distribution tree since itshould already be synchronized with the MBSFN network.

Other than the two scenarios mentioned above, there could be“intermediate scenarios” such as the serving cell eNodeB 210 having thecapability information of the neighbor cells, but not transmitting thisinformation and, instead, only transmitting the neighbor ID list to saveon resources. In this scenario, if the capability information ofneighbor MBMS cells is not transmitted by the serving cell eNode B 210,then the WTRU 205 may have to read the system information to understandwhether the neighbor cell provides the requisite service and theprocedure might be similar as mentioned before in the second scenario.

The overall procedure though could be faster or better controlled thanin the second scenario since this neighbor ID list can act as a whitelist mentioning only the cells which the WTRU 205 is allowed to camp onthereby giving the serving cell eNodeB 210 more control over thereselection procedure, and the serving cell eNodeB 210 could exert somecontrol on the reselection procedures. For example, preference may begiven to some neighbor cells or redirecting to some cells through cellspecific reselection parameters, such as those described in U.S.Provisional application 60/894,588, since it has knowledge of theneighboring cell capabilities.

The serving cell eNodeB 210 has the capability information and ID listof the neighbor cells, but does not transmit the information to save onresources. In this scenario if the capability information and ID list ofneighbor MBMS cells is known but not transmitted by the serving celleNodeB 210, then the WTRU 205 may have to detect the target cell eNodeB215 and read the system information to understand whether the targetcell eNodeB 215 provides the requisite service. The procedure then maybe similar as mentioned before in the second scenario.

The overall procedure though could be faster or better controlled thanin second scenario since knowing the neighbor information can help theserving cell realize it is the border/edge cell of the MBSFN area whichit could then indicate through its broadcast messages. Thus the WTRU 205would expect that the cell it might reselect to might be part of theMBSFN guard area or a part of the non-MBSFN area and could potentiallyuse this information to make its reselection and handover proceduresmore robust.

FIG. 2B is a signal diagram similar to FIG. 2A except that an indicationthrough a broadcast or any other message is sent to the WTRU indicatingthat the target cell eNodeB is ready to start MBMS service (step 295).

FIG. 3A shows a wireless communication system 300 including a WTRU 305,a serving cell eNodeB (non-MBSFN area) 310, a target, (i.e., neighbor),cell eNodeB (non-MBSFN area) 315 and an AGW 320. The WTRU 305 moves fromone non-MBSFN area cell to another non-MBSFN area cell, where neighborcell information and capability information is transmitted by thenon-MBSFN serving cell.

FIG. 3B is a signal diagram similar to FIG. 3A except that the neighborcell information and capability information for the MBMS cells is nottransmitted by the serving cell to the WTRU.

FIG. 4 is a block diagram of a WTRU 400 configured to perform any of theoperations performed by the WTRUs 105, 205 and 305. The WTRU 400includes an antenna 405, a receiver 410, a processor 415 and atransmitter 420.

The receiver 410 is configured to receive cell information associatedwith target cell eNodeBs that neighbor a serving cell eNodeB. Theprocessor 415 is configured to evaluate cell reselection criteria anddetermine a neighboring target cell eNodeB to reselect. The transmitter420 is configured to transmit a RACH preamble or RACH message indicatingthe neighboring target cell eNodeB. The receiver 410 is furtherconfigured to receive and read MIB and system information messages. Theprocessor 415 is further configured to confirm that the determinedneighboring target cell eNodeB is not part of a MBSFN.

The transmitter 420 is further configured to transmit a cell updatemessage including capability information and service requirements. Thereceiver 410 is further configured to receive a cell update confirmationmessage indicating that the neighboring target cell eNodeB is ready toprovide a wireless communication service (e.g., MBMS). The processor 415is further configured to reselect the neighboring target cell eNodeB,and the receiver 410 is further configured to receive an indicationindicating that the neighboring target cell eNodeB is ready to provide awireless communication service (e.g., MBMS).

The processor 415 is further configured to read the MIB messages againto determine whether the received system information has changed, and ifit is determined that the system information has changed, the processor415 reads the system information and reselects to the neighboring targetcell eNodeB

FIG. 5 is a block diagram of an eNodeB 500 configured to perform any ofthe operations performed by the eNodeBs 110, 115, 210, 215, 310 and 315.The eNodeB 500 includes an antenna 505, a receiver 510, a processor 515and a transmitter 520. The eNodeB 500 may be a serving cell eNodeB or atarget cell eNodeB.

If the eNodeB 500 in FIG. 5 is a serving cell eNodeB, the receiver 510is configured to receive cell information associated with target celleNodeBs for a multimedia broadcast single frequency network (MBSFN) areafrom an AGW. The transmitter 520 is configured to transmit the receivedcell information. The receiver 510 is further configured to receive aRACH preamble or RACH message indicating a neighboring target eNodeB.The transmitter 520 is further configured to transmit a signal includingthe identity of a wireless transmit/receive unit (WTRU) and requiredservices information.

If the eNodeB 500 in FIG. 5 is the neighboring target cell eNodeB thatis reselected, the receiver 510 is configured to receive a signalincluding the identity of a WTRU and required services information, andthe processor 515 is configured to determine whether the target celleNodeB has the required services. The transmitter 520 is configured totransmit MIB and system information messages at a periodic rate, and ifthe target cell eNodeB does not have the required services, thetransmitter 520 transmits a message requesting that the target eNodeB bejoined to a multicast distribution tree for providing the requiredservices.

The receiver 510 may be further configured to receive a cell updatemessage including capability information and service requirements, andthe transmitter 520 may be further configured to transmit a cell updateconfirmation message indicating that target cell eNodeB is ready toprovide a wireless communication service (e.g., MBMS). The receiver 510may be further configured to receive a message acknowledging the messagerequesting that the target cell eNodeB be joined to a multicastdistribution tree for providing the required services.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

1. A method of providing wireless communication services, the methodcomprising: receiving, from a serving cell eNodeB, cell informationassociated with target cell evolved Node-Bs (eNodeBs) that neighbor theserving cell eNodeB; evaluating cell reselection criteria; determining aneighboring target cell eNodeB to reselect; transmitting, to the servingcell eNodeB, a random access channel (RACH) preamble or RACH messageindicating the neighboring target cell eNodeB; receiving and readingmaster information block (MIB) and system information messages of theneighboring target cell eNodeB; and confirming that the determinedneighboring target cell eNodeB is not part of a multimedia broadcastsingle frequency network (MBSFN).
 2. The method of claim 1 furthercomprising: reselecting to the neighboring target cell eNodeB;transmitting, to the neighboring target cell eNodeB, a cell updatemessage including capability information and service requirements; andreceiving, from the neighboring target cell eNodeB, a cell updateconfirmation message indicating that the neighboring target cell eNodeBis ready to provide a wireless communication service.
 3. The method ofclaim 2 wherein the wireless communication service is multimediabroadcast multicast services (MBMS).
 4. The method of claim 1 furthercomprising: reselecting to the neighboring target cell eNodeB; andreceiving a signal from the neighboring target cell eNodeB indicatingthat the neighboring target cell eNodeB is ready to provide a wirelesscommunication service.
 5. The method of claim 4 wherein the wirelesscommunication service is multimedia broadcast multicast services (MBMS).6. A wireless transmit/receive unit (WTRU) comprising: a receiverconfigured to receive, from a serving cell eNodeB, cell informationassociated with target cell evolved Node-Bs (eNodeBs) that neighbor theserving cell eNodeB; a processor configured to evaluate cell reselectioncriteria and determine a neighboring target cell eNodeB to reselect; anda transmitter configured to transmit, to the serving cell eNodeB, arandom access channel (RACH) preamble or RACH message indicating theneighboring target cell eNodeB, wherein the receiver is furtherconfigured to receive and read master information block (MIB) and systeminformation messages of the neighboring target cell eNodeB, and theprocessor is further configured to confirm that the determinedneighboring target cell eNodeB is not part of a multimedia broadcastsingle frequency network (MBSFN).
 7. The WTRU of claim 6 wherein thetransmitter is further configured to transmit, to the neighboring targetcell eNodeB, a cell update message including capability information andservice requirements, and the receiver is further configured to receive,from the neighboring target cell eNodeB, a cell update confirmationmessage indicating that the neighboring target cell eNodeB is ready toprovide a wireless communication service.
 8. The WTRU of claim 7 whereinthe wireless communication service is multimedia broadcast multicastservices (MBMS).
 9. The WTRU of claim 6 wherein the processor is furtherconfigured to reselect the neighboring target cell eNodeB, and thereceiver is further configured to receive an indication indicating thatthe neighboring target cell eNodeB is ready to provide a wirelesscommunication service.
 10. The WTRU of claim 9 wherein the wirelesscommunication service is multimedia broadcast multicast services (MBMS).11. A method of providing wireless communication services, the methodcomprising: receiving neighbor cell information and capabilityinformation for a multimedia broadcast single frequency network (MBSFN)area; transmitting, to a wireless transmit/receive unit (WTRU), cellinformation associated with target cell evolved Node-Bs (eNodeBs) thatneighbor a serving cell eNodeB; receiving, from the WTRU, a randomaccess channel (RACH) preamble or RACH message indicating a neighboringtarget eNodeB; and transmitting, to the neighboring target cell eNodeB,a signal including the identity of the WTRU and required servicesinformation.
 12. A serving cell evolved Node-B (eNodeB) for providingwireless communication services, the eNodeB comprising: a receiverconfigured to receive cell information associated with target cellevolved Node-Bs (eNodeBs) for a multimedia broadcast single frequencynetwork (MBSFN) area; and a transmitter configured to transmit, to awireless transmit/receive unit (WTRU), the received cell information,wherein the receiver is further configured to receive, from the WTRU, arandom access channel (RACH) preamble or RACH message indicating aneighboring target eNodeB, and the transmitter is further configured totransmit, to the neighboring target cell eNodeB, a signal including theidentity of the WTRU and required services information.
 13. A method ofproviding wireless communication services, the method comprising:detecting a plurality of target cell evolved Node-Bs (eNodeBs) thatneighbor a serving cell eNodeB; evaluating cell reselection criteria;determining a neighboring target cell eNodeB to reselect; receiving andreading master information block (MIB) and system information messagesof the neighboring target cell eNodeB; transmitting, to the serving celleNodeB, a random access channel (RACH) preamble or RACH messageindicating the neighboring target cell eNodeB; receiving and reading MIBmessages of the neighboring target cell eNodeB again to determinewhether the system information has changed; and if it is determined thatthe system information has changed, reading the system information andreselecting to the neighboring target cell eNodeB.
 14. The method ofclaim 13 further comprising: if reselection to the neighboring targetcell eNodeB occurs, transmitting, to the neighboring target cell eNodeB,a cell update message including capability information and servicerequirements; and receiving, from the neighboring target cell eNodeB, acell update confirmation message indicating that the neighboring targetcell eNodeB is ready to provide a wireless communication service. 15.The method of claim 14 wherein the wireless communication service ismultimedia broadcast multicast services (MBMS).
 16. The method of claim13 further comprising: if reselection to the neighboring target celleNodeB occurs, receiving, from the neighboring target cell eNodeB, asignal indicating that the neighboring target cell eNodeB is ready toprovide a wireless communication service.
 17. The method of claim 16wherein the wireless communication service is multimedia broadcastmulticast services (MBMS).
 18. The method of claim 13 furthercomprising: confirming that the determined neighboring target celleNodeB is not part of a multimedia broadcast single frequency network(MBSFN).
 19. A wireless transmit/receive unit (WTRU) comprising: areceiver configured to detect a plurality of target cell evolved Node-Bs(eNodeBs) that neighbor a serving cell eNodeB; a processor configured toevaluate cell reselection criteria and determine a neighboring targetcell eNodeB to reselect; the receiver further configured to receive andread master information block (MIB) and system information messages ofthe neighboring target cell eNodeB; a transmitter configured totransmit, to the serving cell eNodeB, a random access channel (RACH)preamble or RACH message indicating the neighboring target cell eNodeB;and the processor being further configured to read MIB messages of theneighboring target cell eNodeB again to determine whether the systeminformation has changed, and if it is determined that the systeminformation has changed, the processor reads the system information andreselects to the neighboring target cell eNodeB.
 20. The WTRU of claim19 wherein if reselection to the neighboring target cell eNodeB occurs,the transmitter is further configured to transmit, to the neighboringtarget cell eNodeB, a cell update message including capabilityinformation and service requirements, and the receiver is furtherconfigured to receive, from the neighboring target cell eNodeB, a cellupdate confirmation message indicating that the neighboring target celleNodeB is ready to provide a wireless communication service.
 21. TheWTRU of claim 20 wherein the wireless communication service ismultimedia broadcast multicast services (MBMS).
 22. The WTRU of claim 20wherein the processor is further configured to confirm that thedetermined neighboring target cell eNodeB is not part of a multimediabroadcast single frequency network (MBSFN)
 23. A target cell evolvedNode-B (eNodeB) for providing wireless communication services, thetarget cell eNodeB comprising: a receiver configured to receive, from aserving cell eNodeB, a signal including the identity of a wirelesstransmit/receive unit (WTRU) and required services information; aprocessor configured to determine whether the target cell eNodeB has therequired services; and a transmitter configured to transmit masterinformation block (MIB) and system information messages, and if thetarget cell eNodeB does not have the required services, the transmitteris further configured to transmit a first message requesting that thetarget eNodeB be joined to a multicast distribution tree for providingthe required services.
 24. The target cell eNodeB of claim 23 whereinthe receiver is further configured to receive, from the WTRU, a cellupdate message including capability information and servicerequirements, and the transmitter is further configured to transmit, tothe WTRU, a cell update confirmation message indicating that the targetcell eNodeB is ready to provide a wireless communication service. 25.The target cell eNodeB of claim 24 wherein the wireless communicationservice is multimedia broadcast multicast services (MBMS).
 26. Thetarget cell eNodeB of claim 24 wherein the receiver is furtherconfigured to receive a second message acknowledging the first messagerequesting that the target cell eNodeB be joined to a multicastdistribution tree for providing the required services.